The invention is directed to a lead-free eutectic solder alloy comprising zinc (Zn) as the main component and aluminum (Al) as an alloying metal. The invention is also directed to the use of the lead-free eutectic solder alloy.
Legislation driven by environmental and health concerns is still driving the replacement of lead-containing solder alloys with lead-free alternatives. However, the alternative solder alloy's melting temperature, or to be more precise, its solidus temperature must be high enough, especially with regard to applications in which the finished solder joints experience high temperature as the case may be either in later process steps and/or under field conditions. In die-attach applications, for example, a melting temperature of the solder alloy in the range of 280 to 400° C. is required.
US 2013/0045131 A1 discloses lead-free zinc base solder compositions comprising 82 to 96 wt. % (weight-%) of zinc, 3 to 15 wt. % of aluminum, 0.5 to 1.5 wt. % of magnesium and 0.5 to 1.5 wt. % of gallium.
JP2000208533 A discloses a lead-free zinc base die-bonding alloy of 2 to 9 wt. % of aluminum, 0.01 to 0.5 wt. % of magnesium, 2 to 9 wt. % of germanium and a remainder of zinc and inevitable impurities.
US2012/0313230 A1 claims several lead-free zinc base solder alloys, one with 8 to 20 wt. % of aluminum, 0.5 to 20 wt. % of magnesium and 0.5 to 20 wt. % of gallium, a further one with 1 to 30 wt. % of aluminum, 0.5 to 20 wt. % of magnesium and 0.5 to 6.5 wt. % of tin and also one with 1 to 30 wt. % of aluminum, 0.5 to 20 wt. % of germanium and 0.5 to 20 wt. % of gallium, the rest of the alloys in each case comprising zinc.
JP2012228729 A discloses lead-free zinc base solder alloy comprising 0.01 to 9.0 wt. % of aluminum, at least one of germanium, magnesium, silver and phosphorus in ranges of 0.01 to 8.0 wt. % of germanium, 0.01 to 5.0 wt. % of magnesium, 0.1 to 4.0 wt. % of silver, and at most 0.5 wt. % of phosphorus; and a remainder of Zn and inevitable impurities.
JP11207487 A discloses lead-free zinc base solder alloy consisting of 1 to 7 wt. % of aluminum, 0.5 to 6 wt. % of magnesium, 1 to 25 wt. % of tin, and the balance zinc with inevitable impurities.
US 2013/0251587 A1 claims lead-free zinc base solder alloy consisting of 1.0 to 9.0 wt. % of aluminum, 0.002 to 0.8 wt. % of phosphorus, 0.3 to 3 wt. % of germanium and a balance being zinc with inevitable impurities.